Bacteria, Beware of Nano-Sized Assassins

Staphylococcus epidermidis is quite an opportunist. Commonly found on human skin, the bacteria pose little danger. But S. epidermidis is a leading cause of infections in hospitals. From catheters to prosthetics, the bacteria are known to hitch a ride on a range of medical devices implanted into patients.

Inside the body, the bacteria multiply on the implant's surface and then build a slimy, protective film to shield the colony from antibiotics.

There is no effective antidote for infected implants. The only way to get rid of the bacteria is to remove the implant. "There is no [easy] solution", said Thomas Webster, a biomedical engineer at Brown University.

In lab tests, Webster and Brown graduate student Erik Taylor noted that up to 28 percent of the bacteria on an implant had been eliminated after 48 hours by injecting 10 micrograms of the nanoparticle agents. The same dosage repeated three times over six days destroyed essentially all the bacteria, the experiments showed.

The tests demonstrated "there will be a continual killing of the bacteria until the film is gone," said Webster.

A surprising added benefit, the scientists learned, is the nanoparticles' magnetic properties appear to promote natural bone cell growth on the implant's surface, although this observation needs to be tested further.